diff options
Diffstat (limited to 'fs/bcachefs/util.c')
| -rw-r--r-- | fs/bcachefs/util.c | 24 |
1 files changed, 15 insertions, 9 deletions
diff --git a/fs/bcachefs/util.c b/fs/bcachefs/util.c index e0a876cbaa6b..da2cd11b3025 100644 --- a/fs/bcachefs/util.c +++ b/fs/bcachefs/util.c @@ -653,19 +653,25 @@ int bch2_bio_alloc_pages(struct bio *bio, size_t size, gfp_t gfp_mask) return 0; } -size_t bch2_rand_range(size_t max) +u64 bch2_get_random_u64_below(u64 ceil) { - size_t rand; + if (ceil <= U32_MAX) + return __get_random_u32_below(ceil); - if (!max) - return 0; + /* this is the same (clever) algorithm as in __get_random_u32_below() */ + u64 rand = get_random_u64(); + u64 mult = ceil * rand; - do { - rand = get_random_long(); - rand &= roundup_pow_of_two(max) - 1; - } while (rand >= max); + if (unlikely(mult < ceil)) { + u64 bound; + div64_u64_rem(-ceil, ceil, &bound); + while (unlikely(mult < bound)) { + rand = get_random_u64(); + mult = ceil * rand; + } + } - return rand; + return mul_u64_u64_shr(ceil, rand, 64); } void memcpy_to_bio(struct bio *dst, struct bvec_iter dst_iter, const void *src) |